Conventional cruise control systems seek to maintain vehicle speed at a preset value, which is ordinarily input to the system by an operator of the vehicle. For this purpose, known cruise control systems can include sensors for detecting actual vehicle speed, which is fed to a controller and compared with the desired vehicle speed. The vehicle throttle is then adjusted based on an error signal and a control algorithm. In addition, such systems can also include sensors for detecting obstacles in the path of the vehicle, and for adjusting the vehicle speed accordingly.
One specific known cruise control system is disclosed in U.S. Pat. No. 6,990,401 to Neiss et al., and entitled Predictive Speed Control for a Motor Vehicle. This Neiss et al. patent is understood to disclose a vehicle control system that continually adjusts vehicle control parameters based on some vehicle operating conditions as well as stored route information, using an analytic function to determine an optimal speed for the vehicle. Although such a cruise control system is advantageous, improved cruise control in the face of widely varying vehicle operating conditions and parameters is nevertheless desirable.
Cruise control systems, such as described above, use mathematical models of a vehicle to compute the optimal desired cruise speed. The underlying mathematical model utilizes information about the vehicle model and parameters such as the drag coefficient and rolling coefficient in the cruise control. However, the Neiss et al. patent uses nominal parameter values for a number of these parameters. Under at least certain vehicle operating conditions, there can exist a big mismatch between a model utilizing such nominal parameter values and the actual operation of the vehicle, which can result in inefficient cruise control.